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New Lecture Tab.

I gave a lecture to the internal medicine residents of Saint Johns today. The lecture was case based and focused on non-anion gap metabolic acidosis. Later, I received this e-mail:

Dear Dr Topf,

I appreciate your lecture this morning on Non-anion gap metabolic acidosis, I tried to get a copy from your website, but i couldnt find it. I would appreciate if I could get a copy

Thank you,
Saif

Saif, you want it? You got it.

Look above and next the Blog and Handout tabs is a brand new tab, Lectures.

If the presentation is a powerpoint-style slideshow then I’ll post it under that tab. If the lecture was paper based then look under Handout for the supporting material.

Enjoy.

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Epocrates announces that it is ending support of WebOS

Epocrates got its start in the PDA boom of the late 90’s on the backs of the Palm platform. I am surprised that they are pulling up stakes and dumping WebOS. It feels like HP was too slow in releasing new metal or doing anything to show the developer community that there is a reason to stick it out. Could the last WebOS developer shut off the lights and lock the door when they leave.

Sad day. It’s beginning to feel like just a two horse race, Apple and Google.

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My Apple predictions for 2011

Every year the gadget blogs and podcasts give their predictions for the next year. I’m watch Apple pretty closely and I think I have a pretty good feel for the next year. Here are my predictions for 2011. Let’s see how I do.

iPad

The iPad 2 comes out in April after being announced 2-3 weeks earlier. Not a lot of surptrises. It has front and back face-time cameras, weighs less, goes faster and is thinner. It will have a higher resolution screen that Apple will brand a Retina Display but it will not have the same pixel density of the iPhone 4. There wil be three versions, WiFi only, a 3g version with CDMA and a new 4G LTE version from Verizon, AT&T and eventually Sprint.

The current iPad, with the low resolution screen, no camera will live on as a low cost model at $399. With the upcoming entry of Palm, RIM and Android in to the tablet space Apple will try to suck all the atmosphere from the room by lowering the entry level price as aggressively as possible. This will upset all the other competitors pricing plans and provide less maneuvering room in the price umbrella under the iPad.

By the end of the year Apple will have sold 70 million iPads (total 2010 an 2011 sales) and have a market share of 70+%.

iPhone

iPhone 5 is introduced in June and goes on sale in July. It sports the same form factor as iPhone 4 but has a faster processor, longer battery life, and better front and rear camera. The major new feature is near field communication. Apple sticks with 16 and 32 gb memory options. Prices remain the same.
The Verizon iPhone is introduced with the iPhone 5, the first iPhone 4 for Verizon is the $99 8 gb model introduced along with the iPhone 5. 
The white iPhone makes it first appearance since the 3gs as an iPhone 5.
Apple will sell a 65 million iPhones in 2011.

iOS
iOS 5 focuses on the cloud. Music and movies purchased through iTunes can now be streamed over the net. All devices tied to the same apple ID can stream the content, iMacs, Apple TV, iPods, iPads and iPhones.

iOS 5 also gets over the air updating of the OS and over the air continuous back-up, a internet enabled Time Machine back-up service. This major update will better allow iPads to be used without a computer to tether to.

Document management moves forward allowing seamless management of a single document on an iPad then desktop mac and then an iPhone. The document lives in the cloud with synced copies on all of your apple devices.

iOS 5 also adds new APIs that allow software developers to accept voice control and voice feedback for applications.

iOS 5 allows FaceTime over 3g.

Macintosh
The big story for Mac hardware will be the addition of Lightpeak to replace firewire and display port. By the end of 2011 all Macintosh’s will ship with Lightpeak. RIP Firewire.

MacBook Pros will all go SSDs. There maybe an option for a second drive, a magnetic spinning hard drive but the primary drive will be an SSD. The MacBook will continue to have a spinning hard drive further differentiating the Pro models form the baseline MacBook. This trend will continue across the iMac and MacPro lines both of which will be updated to include an SSD as the primary drive with spinning hard drives as additional drive options.

Video professionals and HD enthusiasts looking for Macs to ship with Blu-Ray will continue to be disappointed. No Blue-Ray drives will ship in any Macintosh’s.

MacOS 10.7 Lion will be announced at WWDC to be introduced in the Fall. 10.7 will introduce a new look and feel with a more iOS-like theme.

The Mac App Store will be a huge hit and will reinvigorate innovation on the PC. The amount of money most people spend on desktop apps will rise and this will intropduce many people to the creativity of the independent Mac Software developer. This will further loosen Microsoft’s and Adobe’s hold on on the software market as people get exposed to a myriad of less expensive, less complex and more focused single purpose applications.

iLife 2011 will add a new application. This application will allow hobbyists, enthusiasts and educators to create interactive content for the iPad. A Hypercard for a new era. See this post.

iPods
In September the big announcement will be that the iPod Nano adopts iOS and becomes the smallest general purpose computer. Apple will open the Nano to a specialized corner of the App store where developer focus on voice and speech for much of the interface.

iPod classic goes away and along with it the last click wheel iPod. The iPod Touch gets a version with 128 gb to replace the lost Classic.

Apple TV adds apps that primarily function as channels. So there is the National Geographic app which allows you to view NG video content on your TV.

Apple
Apple will not release a release a large screen TV or any other sized TV.

They will not make a major acquisition, though they will continue to gobble up small, engineering-focussed companies with core technologies.

The Apple-Google  will not jettison Google or Google Maps.

AAPL will hit a high of $415 and finish the year at $395.

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I’m reading The Immortal Life of Henrietta Lacks

The Immortal Life of Henrietta Lacks is about the HeLa cells and the woman they came from. I’ve just started it but it is really interesting.

One of the most striking parts of the story is hearing how Jim Crow laws and segregation affected medicine. Rebecca Skloot discusses sick black patients coming to a hospital and being turned away to go to a “Colored” hospital and then dying in the parking lot without ever receiving therapy. Hard for me to imagine.

Henrietta and David Lacks

The other interesting story was that of Alexis Carrel the winner of the  1912 Nobel Prize for medicine. His Nobel was for his work in creating a surgical technique for sewing blood vessels together. He is important in the HeLa story as he claimed to have created the first immortal tissue cell culture. This was embryonic chicken heart cells. The heart tissue long outlived the lifetime of the chicken and even outlived Carrel himself but the book states that Carrell faked his results by adding fresh embryonic cells periodically. The book also discredits him as a Nazi sympathizer and a eugenics proponent.

The book is good. I recommend it.

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New Handout Tab.

Look up, just below General Jack Ripper and Group Commander Lionel Mandrake are two new tabs: Blog and Handouts. This fulfills a constant request I get from residents and medical students, how do I get a copy of your handouts. Clicking on Handouts will take you to an index with every handout in PDF and Pages format.

I plan on adding pages for presentations and the Fluid and Electrolyte Companion.

Enjoy.

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Renal week day 4: The case for DDAVP in severe hyponatremia

Today I went to see Richard Stern talk about Therapeutic Considerations in the Hyponatremic Patient. It was an excellent talk. One of the concepts he introduced, at least to me, was the use of DDAVP in the patient with severe hyponatremia.

His argument was that the biggest threat to to these patients is the overly rapid correction of sodium due to the sudden suppression of endogenous ADH in the middle of therapy. This is exactly what I was worried about when I was treating that severe case of hyponatremia a couple of weeks ago. My solution up to now is to write an order for the nurse to call me if the patient’s urine output rises over 100 mL an hour. Unfortunately this is an unusual call order and nurse compliance with it is questionable.

He proposes using DDAVP to essentially lock, or hold constant urinary losses. Then you use 3% saline and the increases in plasma sodium should be more predictable.

This maneuver has a high degree of difficulty but I think it solves an important problem. I’m going to try this on my next case of extreme hyponatremia.

Has anyone else used this technique?

– Posted using BlogPress from my iPad

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If you are going to ASN Renal Week, let’s meet up

It would be fun to put a face on people interested in medical blogging. I am in Denver right now but I’m too stressed about my talk to meet until after noon on Thursday. If anyone is interested leave a comment, and I’ll come up with a location for a casual meeting.

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Lowest sodium I have ever seen

I’m not sure if it is really the lowest sodium but it definately was among the lowest.

I received a call regarding a consult for a patient with a sodium of 105.

The patient is a 60 year old caucasian woman who had been started on chlorthalidone 3 days prior to admission. Her physician had been wrestling with hypertension and changed her from 25 mg of hydrochorothiazide to 50 mg of chlorthalidone. (The internist was keeping up with her American Journal of Hypertension. Though 50 mg is a whole lotta chlorthalidone.)

Both figures are from Ernst Et al. Hypertension 2006

After one or two days of the new diuretic the patient started vomiting and developed diarrhea. The only thing she was able to keep down was water. When she came to the ER she hadn’t eaten anything solid for two days.

She was admitted with hypovolemic hyponatremia. She was given a bolus of 500 mL of normal saline in the ER and the sodium went up to 108. Additionally her potassium was 2.7 and her magnesium and phosphorous were low. She was started on potassium chloride and sodium phosphate prior to being transferred to the ICU. When I called the nurse I was told the intensivist  planned on starting her on 3% saline.
I was immediately worried about overcorrecting her sodium and developing osmotic demyelination syndrome from 3% saline and aggressive correction of her potassium. Tom Berl had come and spoken to our fellow and had put the fear of potassium in me by discussing a case that was triggered by potassium repletion. From the case report:

This patient was at risk of overcorrection because she had two of the most common clinical settings in which such overcorrection occurs: thiazide use and hypovolemia.

Patients with hypovolemic hyponatremia send conflicting signals to the hypothalamus regarding ADH release. The volume deficiency stimulates ADH (if the body volume deficient, let’s not lose any water via the kidneys) and low osmolality surpresses ADH (the body is too diluted so let’s lose some water to bring the concentration up). In the case of this conflict, volume rules. As I tell my medical students,

Remember the ABC’s, Airway, breathing and circulation. O for osmoregulation is way down in the alphabet.

The problem of rapid correction occurs when you correct the volume deficiency and all of the sudden the hypothalamus asks itself, why am I releasing any ADH with an osmolality of 260?

Then the kidney starts producing urine that you could probably bottle and sell as organically filtered water. Electrolyte free water clearance begins to approach the urine output and the sodium also starts to climb and climb fast.

To protect this patient I told the nurse to decrease the normal saline to 100 mL per hour and to call me if the urine output goes over 200 per hour. We also started checking the sodium every six hours and I ordered urine osmolality, sodium and potassium.

Her sodium started to rise slowly, the urine output increased but never resembled Niagra. After two days her sodium was in the 120s her urine still appeared volume depleted and volume status began to look wet. She developed wheezes and she had a few rales. We had to abandon the normal saline. We started tolvaptan. She received 30 mg once and then 15 mg the next day after she had a brisk response. After that her urine electrolytes resembled SIADH.

Once the sodium crossed 130 I stopped the tolvaptan, restricted her free water, and added a gram of sodium chloride twice a day. Her sodium stabilized around 130.

Around this time I sent a renin aldo ratio. I usually order these before I start a patient on aldactone, because after you start it you need to wash them out for weeks prior to checking for primary hyperaldosteronism. Our patient had difficult to treat hypertension and hypokalemia on admission, so I checked it. I just found out that it came back positive. The high aldosterone was after we had corrected her volume deficiency. I think it is primary, and this may explain why she had persistently low urine sodiums despite successful volume resuscitation.

We looked for a cause of the SIADH, but couldn’t find anything. No narcotics, no pulmonary disease, no malignancy, normal TSH and cortisol, no anti-depressants. She had a normal non-contrast head CT scan on admission. I even ordered a contrasted CT scan of the chest to make sure she didn’t have a cancer in there. Nothing. Idiopathic SIADH hiding behind, at least initially, volume depletion and in the background of primary hyperaldosteronism. Strange case.